Panel air filters are generally used for filtering air in forced air systems such as furnaces and ventilation systems. Panel air filters generally comprise a panel of filter media surrounded and supported by a paperboard frame. One common type of filter media used in panel filters is pleated filter media that includes a plurality of peaks and valleys. In most prior art implementations, pleated filter media have used a semi-rigid support structure other than the frame to maintain the shape of the peaks and valleys and prevent the pleats from collapsing or becoming misshapen. For example, triangular shaped wedges interposed between the pleats have been used. Alternatively, the support structure might include a wire mesh often referred to as a scrim that is copleated with the pleats and has memory that retains its shape and increase the rigidity and support of the pleats.
Self supported panel filters are also known, in which the pleated filter media retains it shape and is supported without a scrim or intermittent wedge (e.g. by the paperboard frame itself). For example, the present assignee makes and sells a pleated panel filter sold under the mark X-treme and covered by pending U.S. patent application Ser. No. 11/156,811, filed on Jun. 20, 2005, the entire disclosure of which is hereby incorporated herein by reference thereto. While not limited thereto, the present invention provides an improvement over this design.
Frames for the panel filters are usually formed from one or multiple pieces of folded and adhesively bonded pieces of paperboard. Unfortunately, during manufacturing while the adhesive is curing, the folded panels of the frame tend to relax which can affect the shape and structural strength of the finished frame. While there are attempts to interlock the folded panels of the frame, these attempts have complexities, result in extra manufacturing cost or inefficiency, and/or are not applicable to one piece die cut frames. Such prior designs are also more complex than necessary and unnecessarily use more material than is required to prevent the folded panels from shifting while the adhesive cures.
There are various examples in the prior art relating to the frame teachings of panel filters. One such example is U.S. Pat. No. 4,561,587 to Wysocki. The '587 patent teaches a one piece paperboard frame having a plurality of foldable panels that are interconnected at fold lines. However, the '587 patent requires a complex shape that uses numerous unnecessary panels, which increases the amount of material required for the blank of paperboard and the amount of time for assembling the frame member. Furthermore, another example of a one-piece paperboard blank that can be folded into a panel filter frame includes U.S. Pat. No. 4,570,844 also to Wysocki. The '844 patent includes four separate foldable panels on each side of a main panel all interconnected at fold lines. The foldable panels on adjacent sides of the main panel are interconnected to secure the frame in a folded position. However, by using four panels on each side, when the panels are folded, they provide duplication of panels that extend substantially perpendicular to the main panel. This configuration further uses increased amount of material and makes the design complex. Additionally, another example of a paperboard panel filter frame includes U.S. Pat. No. 4,323,379 to Shearin. The frame in Shearin provides a substantially elongated strip that wraps around the perimeter of a piece of filter media and does not pertain to a one piece die cut including an integral grill or main panel that extends across the surface of the filter media.
There exists, therefore, a need in the art for an improved one-piece panel filter frame and panel filter that is simple in design, easily manufactured and uses a minimum of material and foldable flaps while providing interlocking panels. Furthermore, there exists a need in the art for a pleated panel filter with an improved frame in which the pleated filter media is self supporting without the use of additional rigid material or interposed support members, further reducing the complexity of the panel filter.